#include <vector>
#include <string>
#include <sstream>

#include <Poco/MongoDB/Connection.h>
#include <Poco/MongoDB/Cursor.h>
#include <Poco/MongoDB/Element.h>

#include <DB/Dictionaries/DictionaryStructure.h>
#include <DB/Dictionaries/MongoDBBlockInputStream.h>
#include <DB/DataTypes/DataTypesNumber.h>
#include <DB/DataTypes/DataTypeString.h>
#include <DB/DataTypes/DataTypeDate.h>
#include <DB/DataTypes/DataTypeDateTime.h>
#include <DB/Columns/ColumnString.h>
#include <DB/Columns/ColumnsNumber.h>
#include <ext/range.hpp>
#include <DB/Core/FieldVisitors.h>


namespace DB
{

MongoDBBlockInputStream::MongoDBBlockInputStream(
	std::shared_ptr<Poco::MongoDB::Connection> & connection_,
	std::unique_ptr<Poco::MongoDB::Cursor> cursor_,
	const Block & sample_block,
	const size_t max_block_size)
	:  connection(connection_), cursor{std::move(cursor_)}, max_block_size{max_block_size}
{
	description.init(sample_block);
}


MongoDBBlockInputStream::~MongoDBBlockInputStream() = default;


String MongoDBBlockInputStream::getID() const
{
	std::ostringstream stream;
	stream << cursor.get();
	return "MongoDB(@" + stream.str() + ")";
}


namespace
{
	using ValueType = ExternalResultDescription::ValueType;

	template <typename T>
	void insertNumber(IColumn * column, const Poco::MongoDB::Element & value, const std::string & name)
	{
		switch (value.type())
		{
			case Poco::MongoDB::ElementTraits<Int32>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().push_back(static_cast<const Poco::MongoDB::ConcreteElement<Int32> &>(value).value());
				break;
			case Poco::MongoDB::ElementTraits<Int64>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().push_back(static_cast<const Poco::MongoDB::ConcreteElement<Int64> &>(value).value());
				break;
			case Poco::MongoDB::ElementTraits<Float64>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().push_back(static_cast<const Poco::MongoDB::ConcreteElement<Float64> &>(value).value());
				break;
			case Poco::MongoDB::ElementTraits<bool>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().push_back(static_cast<const Poco::MongoDB::ConcreteElement<bool> &>(value).value());
				break;
			case Poco::MongoDB::ElementTraits<Poco::MongoDB::NullValue>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().emplace_back();
				break;
			case Poco::MongoDB::ElementTraits<String>::TypeId:
				static_cast<ColumnVector<T> *>(column)->getData().push_back(
					parse<T>(static_cast<const Poco::MongoDB::ConcreteElement<String> &>(value).value()));
				break;
			default:
				throw Exception("Type mismatch, expected a number, got type id = " + toString(value.type()) +
					" for column " + name, ErrorCodes::TYPE_MISMATCH);
		}
	}

	void insertValue(
		IColumn * column, const ValueType type, const Poco::MongoDB::Element & value, const std::string & name)
	{
		switch (type)
		{
			case ValueType::UInt8: insertNumber<UInt8>(column, value, name); break;
			case ValueType::UInt16: insertNumber<UInt16>(column, value, name); break;
			case ValueType::UInt32: insertNumber<UInt32>(column, value, name); break;
			case ValueType::UInt64: insertNumber<UInt64>(column, value, name); break;
			case ValueType::Int8: insertNumber<Int8>(column, value, name); break;
			case ValueType::Int16: insertNumber<Int16>(column, value, name); break;
			case ValueType::Int32: insertNumber<Int32>(column, value, name); break;
			case ValueType::Int64: insertNumber<Int64>(column, value, name); break;
			case ValueType::Float32: insertNumber<Float32>(column, value, name); break;
			case ValueType::Float64: insertNumber<Float64>(column, value, name); break;

			case ValueType::String:
			{
				if (value.type() != Poco::MongoDB::ElementTraits<String>::TypeId)
					throw Exception{
						"Type mismatch, expected String, got type id = " + toString(value.type()) +
							" for column " + name, ErrorCodes::TYPE_MISMATCH};

				String string = static_cast<const Poco::MongoDB::ConcreteElement<String> &>(value).value();
				static_cast<ColumnString *>(column)->insertDataWithTerminatingZero(string.data(), string.size() + 1);
				break;
			}

			case ValueType::Date:
			{
				if (value.type() != Poco::MongoDB::ElementTraits<Poco::Timestamp>::TypeId)
					throw Exception{
						"Type mismatch, expected Timestamp, got type id = " + toString(value.type()) +
							" for column " + name, ErrorCodes::TYPE_MISMATCH};

				static_cast<ColumnUInt16 *>(column)->getData().push_back(
					UInt16{DateLUT::instance().toDayNum(
						static_cast<const Poco::MongoDB::ConcreteElement<Poco::Timestamp> &>(value).value().epochTime())});
				break;
			}

			case ValueType::DateTime:
			{
				if (value.type() != Poco::MongoDB::ElementTraits<Poco::Timestamp>::TypeId)
					throw Exception{
						"Type mismatch, expected Timestamp, got type id = " + toString(value.type()) +
							" for column " + name, ErrorCodes::TYPE_MISMATCH};

				static_cast<ColumnUInt32 *>(column)->getData().push_back(
					static_cast<const Poco::MongoDB::ConcreteElement<Poco::Timestamp> &>(value).value().epochTime());
				break;
			}
		}
	}
}


Block MongoDBBlockInputStream::readImpl()
{
	if (all_read)
		return {};

	Block block = description.sample_block.cloneEmpty();

	/// cache pointers returned by the calls to getByPosition
	std::vector<IColumn *> columns(block.columns());
	const size_t size = columns.size();

	for (const auto i : ext::range(0, size))
		columns[i] = block.safeGetByPosition(i).column.get();

	size_t num_rows = 0;
	while (num_rows < max_block_size)
	{
		Poco::MongoDB::ResponseMessage & response = cursor->next(*connection);

		for (const auto & document : response.documents())
		{
			++num_rows;

			for (const auto idx : ext::range(0, size))
			{
				const auto & name = description.names[idx];
				const Poco::MongoDB::Element::Ptr value = document->get(name);

				if (value.isNull())
					insertDefaultValue(columns[idx], *description.sample_columns[idx]);
				else
					insertValue(columns[idx], description.types[idx], *value, name);
			}
		}

		if (response.cursorID() == 0)
		{
			all_read = true;
			break;
		}
	}

	if (num_rows == 0)
		return {};

	return block;
}

}